The present invention relates generally to printers which deposit marks on a recording medium to form images thereon and, more particularly, to a pre-print treatment of the recording media to enhance the print quality of the printed image.
Ink jet printers of the so-called "drop-on-demand" type have at least one printhead from which droplets of ink are directed towards a recording medium. Within the printhead, the ink is contained in a plurality of channels and energy pulses are applied to transducers to cause the droplets of ink to be expelled, as required, from nozzles at the ends of the channels.
In a thermal ink jet printer, the energy pulses are usually produced by resistors, which are individually addressable by current pulses to heat and vaporize ink in a channel or recess proximate to the nozzle. As a vapor bubble grows, ink bulges from the nozzles until the current pulse has ceased and the bubble begins to collapse. At that stage, the ink within the channel or recess retracts and separates from the bulging ink which forms a droplet moving in a direction away from the nozzles and towards the recording medium. The channel or recess is then re-filled by capillary action, which in turn draws ink from a supply cartridge. Operation of a thermal ink jet printer wherein the ink is expelled from channels is described in, for example, U.S. Pat. Nos. 4,638,337 and 4,774,530, which disclose a printer of the carriage type having a plurality of printheads, each with its own ink supply reservoir, mounted on a reciprocating carriage. The nozzles of each printhead are aligned perpendicular to the line of movement of the carriage and a swath of image information is printed on the stationary recording medium as the carriage is moved in one direction. The recording medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to the width of the printed swath and the carriage is then moved in the reverse direction to print another swath of information.
Many forms of recording media are known in the art. Special forms of coated paper are used to provide enhanced optical density and waterfastness. See, for example, U.S. Pat. No. 5,457,486 and the references summarized in columns 1-3. The various coated paper configurations add expense to the printing process, and the great majority of output prints are produced on non-coated plain paper. Because of the low cost of paper, it is widely used in spite of several problems with the quality of images printed thereon. Because the images are formed of aqueous based ink droplets falling onto an absorbent substrate, problems are created such as raggedness along the edges of the image; intercolor bleed (when printing more than one color), line "blooming", optical density and image permanence.
It has been appreciated that application of heat to plain paper, either before, during or after the printing, helps to alleviate some of the above-identified problems. U.S. Pat. No. 5,428,384 discloses use of a preheated drive roller to drive some moisture out of the paper and elevate the paper temperature to reduce paper cockle and curl. A post-heat blower dries the ink rapidly after being deposited on the recording media to help reduce smearing.
U.S. Ser. No. 08/523,322 filed on Aug. 30, 1995 and assigned to the same assignee as the present invention, utilizes a segmented flexible heater to pre-condition the record medium prior to entering the print zone. U.S. Pat. No. 5,380,769 discloses forming an ink image on a substrate; applying a release agent to the image and transferring the image to a recording medium at a fusing station.
Copending application U.S. Ser. No. 09/069,111 assigned to the same assignee as the present invention, filed concurrently herewith, with the named inventors Thomas W. Smith, Samuel Kaplan, Kathleen M. McGrane, and David J. Luca, the disclosure of which is totally incorporated herein by reference, disclose a process which comprises (a) applying to a substrate a fixing fluid which comprises a material selected from the group consisting of (1) block or graft copolymers of dialkylsiloxanes and polar, hydrophilic monomers capable of interacting with an ink colorant to cause the colorant to become complexed, laked, or mordanted, (2) organopolysiloxane copolymers having functional side groups capable of interacting with an ink colorant to cause the colorant to become complexed, laked, or mordanted, (3) perfluorinated polyalkoxy polymers, (4) perfluoroalkyl surfactants having thereon at least one group capable of interacting with an ink colorant to cause the colorant to become complexed, laked, or mordanted, and (5) mixtures thereof; (b) incorporating into an ink jet printing apparatus an ink composition which comprises water and a colorant which becomes complexed, laked, or mordanted upon contacting the fixing fluid; and (c) causing droplets of the ink composition to be ejected in an imagewise pattern onto the substrate.
Copending application U.S. Ser. No. 09/069,110 assigned to the same assignee as the present invention, filed concurrently herewith, with the named inventors Thomas W. Smith, John S. Facci, Michael J. Levy, and David J. Luca, the disclosure of which is totally incorporated herein by reference, discloses a fluid deposition apparatus comprising (a) a fluid supply, (b) a porous fluid distribution member in operative connection with the fluid supply, enabling wetting of the fluid distribution member with a fluid, and (c) a porous metering membrane situated on the fluid distribution member, whereby the metering membrane enables uniform metering of the fluid from the fluid distribution member onto a substrate.